The present invention relates to a magnetic disc apparatus, and more particularly to a magnetic head supporting assembly for use in a magnetic disc apparatus.
FIG. 1 illustrates one example of a conventional magnetic disc apparatus and FIG. 2 illustrates, partly in an enlarged sectional view, a principal portion of a magnetic head supporting assembly for use in the magnetic disc apparatus. Such a conventional magnetic disc apparatus is disclosed in U.S. Pat. No. 4,307,425.
The conventional magnetic disc apparatus comprises a magnetic disc drive assembly 20 mounted on a base (not shown) and a magnetic head supporting assembly 30 disposed on the base in a predetermined positional relationship with respect to the magnetic disc drive assembly 20. The magnetic disc drive assembly 20 comprises a rotary shaft 21 for supporting a pair of vertically spaced magnetic discs 4a and 4b as shown in FIG. 2 and a motor 22 for rotatably driving the rotary shaft 21. The magnetic head supporting assembly 30 comprises a rotary actuator 31 including a rotary shaft 5 which is pivotably mounted thereto and an actuator arm 3 which is secured to the rotary shaft 5. The actuator arm 3 has a pair of mounting members 32, each extending from one end of the actuator arm 3. The head supporting assembly 30 further comprises two pairs of suspension arms 2, each pair inwardly extending from one side of the mounting member 32 of the actuator arm 3. Each suspension arm 2 resiliently supports at the extending end thereof a magnetic head 1 by which magnetic recording and reproducing are achieved on the disc 4. The actuator arm 3 is swingably driven about the rotary shaft 5 by the rotary actuator 31 to move the suspension arms 2 in parallel with the surfaces of the discs 4a and 4b thereby positioning each of the magnetic heads 1 over a desired position of the magnetic discs 4a and 4b.
In the thus-constructed conventional apparatus, the suspension arm 2 is made of an elastic material and is disposed at a predetermined angle with respect to the surface of the disc 4, thereby pressing the head 1 against the surface of the disc 4 by means of its elasticity. When the disc 4 is rotated, an air flow is generated over the surface of the disc 4. When the disc 4 rotates at a high speed, the floating force of the head 1 produced by the air flow is greater than the pressing force of the suspension arm 2, whereby the head 1 is lifted up from the surface of the disc 4 and a small air gap results between the head 1 and the surface of the disc 4. During this time, the magnetic head 1 can move over the surface of the disc 4 in accordance with the movement of the actuator arm 3.
The disc 4 is coated with a resinous material for protecting a magnetic layer thereon. When the disc is stopped, the magnetic head 1 is pressed against the resinous surface of the disc 4 due to the elasticity of the suspension arm 2. Accordingly, it is possible for the head 1 and the surface of the disc 1 to stick to each other.
The thus-constructed conventional magnetic disc apparatus uses a contact-start-stop system. Namely, first, when the disc is stopped, the head 1 is in contact under pressure with the surface of the disc 4 due to the elasticity of the suspension arm 2. Then, when the disc 4 starts rotating, the head 1 is lifted up by the floating force generated by the air flow produced over the surface of the disc 4 as the rotation speed of the disc increases and when the disc 4 is stopped, the head 1 contacts again the surface of the disc 4 as the rotation speed of the disc decreases. This is referred to as a CSS system hereafter.
When the apparatus is not in operation, the head 1 is in contact with the surface of the disc under pressure and stuck to the disc surface, as stated above. When the disc starts to rotate, the head 1 may scratch the surface of the disc 4, since the head 1 contacts the disc 4 at low rotational speeds, whereby the head 1 and the disc 4 may be damaged. Accordingly, the lifetime of the apparatus using the CSS system is limited and the head 1 and the disc 4 are restricted to expensive materials, which results in an expensive magnetic disc apparatus.